March 2004 Chuck DiMarzio, Northeastern University 10471-14-1 ECEU692 Subsurface Imaging Course...

March 2004 Chuck DiMarzio, Northeastern University 10471-14-1

ECEU692Subsurface Imaging

Course NotesPart 14: A Pause to Reflect

Profs. Brooks and DiMarzio

Northeastern University

Spring 2004


From Our First Lecture...

• Some Examples

• Some Technologies

• NSF Center; CenSSIS at NU

• Taxonomies and Architectures of the Field


Some SSI Examples• Landmine Detection [Acoustic, GPR, EM, NQR]• Tunnel and Bunker Detection [Acoustic, GPR, EM]• Excavation Planning [Acoustic, GPR, EM]• Luggage Screening [X-Ray, NQR]• Ocean Imaging [HSI]• Breast Tumor Detection and Classif.[X-Ray, US, DOT]• Stroke Differentiation [DOT, MRI]• Functional Brain Imaging [DOT, MRI]• Cardiac Imaging [Ultrasound, EKG]• Retinal Imaging [HSI, Vis]• Vulnerable Plaque in Coronary Artery [Vis, US, OCT]• Fetal Imaging [DOT, Ultrasound]


Model Subsurface Problems• Problem Geometry

– A* Looking through one material to see another which is below it.

– B* Looking through one material to find inhomogeneities in it.

• Application Areas– 1* Air/Space, 2* Terrestrial, 3* Ocean,

4* Medical, 5* Biological

* Letters and Numbers Refer to Next Slide


Model Subsurface Problems1 Air/Space 3 Ocean2 Terestrial 4 Medical 5 Biological

Landuse

AtmosphericGasses

LandmineDetection

Pollution Mapping

Dermatology

FunctionalBrain Mapping

ExcavationPlanning

MappingMitochondria

ICM CellCounting

A

B

CORAL CORAL REEFSREEFS

SeabedMapping

River River PlumePlume


Example Problems for the Course

• Geometries– Semi-Infinite Slab Lab in HW2– Two-Layers HW3– Embedded Object Lab in HW4

• SSI Technology– Hyperspectral Imaging Lab in HW2

• Coursework– Experiments– Analysis


Some SSI Technologies

• X-Ray• Light (UV, Visible, Infrared)• Ground-Penetrating Radar• Electrical Impedance Tomography• Magnetic Resonance Imaging• Acoustics and Ultrasound• Electromagnetic Sensors• Passive Electromagnetic Imaging• Seismics• Others

~Wavelength


Different Types of Waves

100

105

1010

1015

102010

-4

10-2

100

102

104

106

108

f, Frequency, Hz.

k/(2

), W

aven

umbe

r, m

-1

Sound

(Real)

DPDW

Light(Real)

(Imag)(Imag)

10059_1

1m

1mm

1km

1mm

mm

cm

m

km


10471-15-1.jpg

Wave Behavior

• Absorption

• Reflection

• Refraction

• Diffraction

• Interference

• Scattering Thanks to Emmanuel Bossy, BU

Remember HW 1?


Light in Skin and More

keratinocytes

melanocytes

collagen andelastin

StratumCorneum,5-10m

Epidermis,50-100m

Dermis,few mm

Basal cell cancer (RCM)

Optical Imaging

Vis NIR

Diffusive Imaging

NIRVis


Probe system

1. Definition & Scope of SSIProbe(s) 1 2 .. I

Medium & object are characterized by physical properties, to which the probe waves are sensitive.

One or more probestransmit one or more waves, which are launched into themedium after processing by some probe system.The waves are characterized by their location, power, frequency, waveform, polarization, etc

One or more detectorscharacterized by theirlocation, sensitivity, or noise, detect the waves after processingby some detector system

1 2 .. J Detector(s)

Detector system

objectMedium

Thanks to Prof. Bahaa Saleh, Chair of ECE at Boston University for the concept for this and following slides.


Examples of wave-dependent properties

• Density• Compressibility

Acoustic

• Dielectric constant• Conductivity• Nuclear spin

Electromagnetic

• Refractive index• Absorption coeff. • Fluorescence

Optical

• Absorption

X-Ray

Electrical/Magnetic

• Conductivity• Permeability

Particle BeamsElectron,Positron,..

• Scattering• Emission of x-ray or• secondary emission

Thanks to Prof. Bahaa Saleh


Density, Porosity, Stiffness Chemical composition, pH Metabolic information Ion concentration Physiological changes (e.g., oxygenation) Extrinsic markers (dyes, chemical tags)

Examples of Underlying Parameters

Goals of SSI• Estimate

– Distribution of Measured Parameters or

– Underlying Parameters Related to Them, or

– Object Shape or Features or

• Detect the Presence of a Target or

• Classify Objects Based on Measured Parameters



Rough Surface

Inhomogeneous/Layered

MediumMedium

Absorption

Dispersion

Scattering

Diffusion

Clutter

Electro-magnetic

Optical/IR

X-rayAcoustic

CW Pulsed Modulated

CoherentMulti-

Spectral

Classical Quantum

Outside Inside Auxiliary

PartiallyCoherent

ObjectObject

Nonlinear Absorption

ScatteringNonlinear Scattering

DiffusivePhase Object

Depolarizing

Stationary Moving

Absorption Fluorescence

ProbeProbe

Taxonomy of SSI .object

Medium

Surface

Probes Detectors

Thanks to Prof. Bahaa SalehThanks to Prof. Bahaa Saleh


i

ij

Transmitter (Probe) & Receiver (detector) Patterns j

Probe Pattern: Region in the medium occupied by the probe wave, in the absence of the target & clutter

Detector Pattern: Region in the medium to which the detector is sensitive, I.e., , if a source were to exist within this medium, it would be detected.

Architectures of SSI



1 2 .. I 1 2 .. J

Probe System

Detector System

Interaction regions {ij} are small & do not overlap significantly

Localized SSI Tomograhic SSI

i j

ij

1 2 .. I 1 2 .. J

Probe System

Detector System

i j

ij

LP MVT

Interaction region Vij = region in the medium to which the

signal of detector j is sensitive, when probe wave i is active

Interaction regions {ij} are large & do overlap significantly

Localized vs Tomographic SSI



Transverse ScanningAxial Scanning

Transverse GazingAxial Scanning

Example i) Distributed Probe/ Localized Detection

LP


Example: Photography


Good transverse resolution Poor axial resolution

LP

Example ii) Localized probe/ distributed (bucket) detection


Two-Photon ScanningLaser Microscopy


Both axial & transverse resolution

LP

Example iii) Confocal probe and detection



Transverse resolution by scanningAxial resolution by time of flight sectioning

Example iv) Pulsed Coaxial probe and detection

LP



Computed transverse & axial resolution

MVT

Example v) Axial Tomography



Generally poor axial and transverse resolution

Example vi) Diffusive Photon Density Waves


Transmission Reflection


Generally poor axial and transverse resolution

Example vii) Time-Domain Photon Migration

Transmission Reflection


Why Did We Choose What We Did?

• It’s at least somewhat representative of the scope of SSI

• We know it well

• It allows you to explore problems in depth

• It allows you to do some experiments in our labs

March 2004 Chuck DiMarzio, Northeastern University 10471-14-1 ECEU692 Subsurface Imaging Course...

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